The goal of the project in this grant application is to understnad the molecular mechanisms underlying the development of basal cell cancer. Specifically, they focus their research in the potential role of Gli1 in inducing BCC development and in the understanding of the mechanisms regulated by this zinc finger transcription factor. They have previously shown that Gli1, but not Gli3, is consistently expressed in human sporadic BCCs and that it is sufficient to induce epidermal tumor formation in the skin of frog embryos. Because Gli1 is a target and mediator of Sonic hedgehog (Shh) signaling, Gli1 transcription represents the activation of the Shh signaling pathway. This is consistent with previous findings in which the gene Patched, encoding a transmembrane receptor for Shh having a negative effect on the pathway, is mutated in familial BCCs. Mutations in Patched are thought to be responsible for the Basal cell Nevus Syndrome. They propose to test for the role of Gli2 in BCC formation using the frog embryo assay and to test for the prevalence of its expression in sporadic human BCCs. In addition, they propose to develop a mouse model for BCC formation by the generation of an inducible Gli1 protein in transgenic mice. Finally, they propose to create an in vivo reporter assay for Gli1 function. The experiments are designed to provide a good model to study the molecular basis of BCC formation which may offer the opportunity to develop anti-cancer agents in the future. In addition, understanding how deregulation of the Shh signaling pathway and Gli1 function lead to BCC formation, will shed light into the normal role of this gene in follicle development.